Plant morphology

 

Morphology teaching in the past

An effective way to study and name a flowering plant is to dissect it. Flower part can easily be removed, ovary sectioned to reveal placentation, number of carpels/ stamens and ovary position. This would unable to give clues of its unique characters and why it makes it distinct from closely related species. Those two specimen were part of a botany exercise taught in 1897 to pharmacist. Instead of drawing the dissection the students were pressing them and adding to a mounted specimen showing all the reason behind their choice of family and species.

Iridaceae

Iris foetidissima Stinking Iris

Dissections from top to bottom

1: Perianth pieces and stamen showing attachment of stamen
2: Transverse section of ovary, showing three cells
3: Pistil showing Stigma, style and ovary
4: Stigma and stamen showing position of stamen

Reasons for Order: Three stamens, Perianth six parts, 3 petal like stigmas, Inferior ovary.

Reasons for species: Sword shaped leaves, smell. stamens underneath the stigmas

Leguminosae

Vicia cracca Tufted Vetch

Dissections from top to bottom.

1.Flower ;2.Standard; 3.Wings; 4.Keel; 5.Stamens and Pistil; 6.Fruit; 7.Tendril

Reasons for Order: Papilionaceous Flowers, Stamens 10, fruit a pod

Reasons for species: Tendrils at the end of leaves, Leaflets opposite, Flowers in dense spikes

Nowadays we would draw the specimen and dissections and translate it into a floral formula and Floral diagram.

Species known to science are now much wider than they use to be and this requires to use more complex and large keys found in many different Floras.

Habit

Characteristic mode of growth; general form or shape of a plant - e.g., caespitose, Herb, Scapose, Shrub, Tree, perennial, annual, bulbous...

 

Plants Habit (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

 

Words to describe branches and stem direction growth: Reflexed, recurved, spreading, ascending, sub-erect, appressed, prostrate, decumbent, erect.

 

Stem direction (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

 

Architecture: Description of branching patterns in plants.

 

examples of tree architecture (Adrian D.Bell 'Plant Form' new ed. Timber press 2008)

 

Monopodial and sympodial Growth: The framework of a plant is built up of a number of branches. A single branch, regardless of age or size, must be constructed in one of two ways. It can be developed by the vegetative extension of one apical meristem to form a single shoot or shoot unit. Alternatively the axis is built up by a linear series of shoots unit, with each new distal shoot unit developing from an axillary bud (subterminal or pseudoterminal bud) sited on the previous shoot unit. The whole axis then constitutes a sympodium, formed by sympodial growth.

 

Sympodial and monopodial growth (Adrian D.Bell 'Plant Form' new ed. Timber press 2008)

 

Habitat: Natural setting or abode of a plant, generally specified as a plant community or set of environmental features.

Roots

Underground structure of a plant, generally branched, without appebdages, generally growing into the ground from the base of a stem. Its functions include anchorage, absorption of water and nutrients, and food storage.

Fibrous roots: Composed of fine slender structures. Having a root system composed of many roots similar in lenght and thickness, as in grasses.

Parasitic roots: A plant that benefits from a physical connection to a host plant of another species and often in time harms the host.

Pneumatophores: an air-vessel; an organ containing aerenchyma; in particular, a root of a mangrove plant, growing above the substratum.

Taproot: Main, tapered root that generally grows straight into soil and has smaller, lateral branches.

Tuberous root: Short, thick, fleshy, underground root for storage.

vellum: a membranous covering; a veil. Usually found on adventitous Orchidaceae roots.

Stems

Axis or axes of a plant, bearing appendages such as leaves, axillary buds, and flowers. Sometimes below ground. Can be divided into nodes and internodes.

Bulb: Short underground stem and the fleshy leaves of leaf bases attached to abd surrounding it. - e.g. and onion.

Caudex (caudices): Short, sometimes woody, more or less vertical stem of a perennial, at or beneath ground level.

Corm: Short, thick, unbranched, underground stem often surrounded by dry (not fleshy) leaves or leaf bases. (e.g. Cyclamen)

Prickle: Superficial, sharp pointed projection, derived from epidermis, bark etc...e.g.- Rosa

Rhizome: Underground, often elongated, more or less horizontal stem. Distinguished from root by presence of leaves, leaf scars, scales, buds, etc...

Scape: Pertaining to a plant or an inflorescence having relatively long peduncle that arises from ground level, often from a rosette, sometimes bearing bracts but without leaves.

Spine: Sharp-pointed projection, derived from leaf or other organ.

Stolon: Runner; a normally thin, elongate stem lying more or less flat on the ground and forming roots as well as erect stems or shoots at generally widely spaced node.

Thorn: Sharp pointed branch.

Tuber: Short, thick, fleshy, underground root for storage. swollen rhizome (e.g. potato)

Leaves

Stem appendages with a structure such as a bud, branch, or flower in its axil, generally green and often composed of a stalk (petiole) and a flat, expanded, photosynthetic area (blade).

 

Leaf morphology and divisions (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

 

Stipules, stipels: Appendage at base of petiole, generally paired, variable in form but often leaf- or scale-like, sometimes a spine. Stipel is an appendage at base of a leaflet petiolule.

Leaves can be simple or compound (pinnate, pinnatifid, lobed, palmate, pinnate, even and odd pinnate)

 

branch description and phyllotaxy (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

 

Phyllotaxy: describes the organisation of the leaves on the stem that can be opposite, alternate, decussate, whorled...

Ptyxis: describes how the leaf is folded in the bud. It can be circinate like in Ferns, involute, plicate, convolute....Leaves organisation can also be described using the same terms.

 

Folding of leaves together (Adrian D.Bell 'Plant Form' new ed. Timber press 2008)

 

Leaf margin: The edge, generally of a leaf or perianth part. It can be serrate, toothed...

 

Leaf shape and margin (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

 

Leaf shape: Many terms can be used to describe leaf shape from linear to ovate. The blade base and apex can both be described using the same words from cordate to cuneate.

 

Leaf base shape and petiole (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

 

Pulvinus: a swelling at the base of the stalk of a leaf or leaflet, often glandular or responsive to touch.

venation: Tissue specialized fro transport of substances within a plant. This can be parallel, palmate, reticulate, net-veined, with veins ending or not in teeth or not...

 

Leaf venation (Adrian D.Bell 'Plant Form' new ed. Timber press 2008)

 

Indumentum

the epidermal appendages, e.g. hairs or scales, collectively.

Hairs are very variable and can take many different forms. There are two main types: Unicellular and multicellular. Amongst them we can list: Forked, glandular, stellate, dendritic, peltate, stinging in Urtica, plumose, barbed...

Leaf surface can also be described abaxially (underneath) and adaxially (above) with words like granular, papillate, puberulent, strigose, tomentose, lanate...

 

Indumentum and leaf surfaces (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

 

Inflorescence

An entire cluster of flowers and associated structures. e.g., axes, bracts, bractlets, pedicels.Often difficult to define as to type and boundaries but generally excluding full-sized foliage leaves.

 

Corolla shapes and inflorescences (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

Panicle: Branched inflorescence in which the basal or lateral flower (or some of them) open before the terminal or central flowers on any axis. Undeterminate inflorescence

Cyme: Branched inflorescence in which the central or uppermost flower opens before the peripheral or lower-most flowers on any axis. Determinate inflorescence.

Umbel: Inflorescence in which three to many pedicels radiate from a common point. May be compound, in which case larger inflorescence branches (rays) also radiate from a common point. Characteristic of but not confined to Apiaceae.

Head: Dense, often spheric inflorescence of sessile or subsessile flowers.

Raceme: Unbranched inflorescence of pediceled flowers that open from bottom to top.

Spike: Unbranched inflorescence of sessile flowers, nearly alaways opening from bottom to top.

Corymb: a racemose inflorescence in which the pedicels of the lower flowers are longer than those of the flowers above, bringing all flowers to about the same level.

Catkin: Spike of unisexual flowers with inconspicuous perianths, sometimes pendent and often with conspicuous bracts.

Flowers

 

Flowers (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

 

Perianth: Calyx and corolla collectively, wether or not they are distinguishable.

Calyx: Collective term for sepals; outermost or lowermost whorl of flower parts, generally green and enclosing remainder of flower in bud. Sometimes indistiguishable from corolla. Tepals.

 

Calyx of Viola cornuta hybrid note the 5 sepals, 2 of them have a short spur.

 

Corolla: Collective term for petals; whorl of flower parts immediately inside or above calyx, often large and brightly colored. Sometimes indistinguishable from calyx. Corolla shape can be very variable. Asymmetric, bilateral, biradial, radial, funnel-shaped, salverform, rotate, bellshape, urn-shape....

 

Corolla of Viola cornuta hybrid note the asymetrical or zygomorphic corolla with 5 free petals. The corolla mouth has yellow and darker lines markings.

 

Androecium: Collective term for stamens: Male reproductive structure of a flower, typically composed of a stalk-like filament and a terminal, pollen-producing anther. Anther divided into 2 thecae and 4 pollen sacs. Each thecae open usually along a single slit. Filaments sometimes fused partly fused to the corolla, or to other filaments to form a tube.

 

Androecium of Viola cornuta hybrid note the extended connective, short filament and spur on the back of two of the stamens.

 

Gynoecium or Pistil: Female reproductive structure of a flower, composed of an ovule-containing ovary at the base, one or more pollen-receiving stigmas at the tip, and generally one or more styles between ovary and stigmas. A flower may have one or more simple pistils (each a single, free carpel with a single ovary chamber, placenta, and stigma) or one compound pistil (two or more fused or partially fused carpels, the exact number often equaling the number of ovary lobes, ovary chambers, placentas, styles, or stigmas).

 

Gynoecium of Viola cornuta hybrid note the bent style at the base and globular shape stigmas with secondary pollen presenter.

 

Ovary position: The ovary can be inferior, superior or semi inferior. Inferior ovaries are usually surounded in a structure than can be formed from the stamens, sepals, petals or receptacle and which is called the hypanthium.

 

Two hypothesis of the hypanthium and the inferior ovary developement.

 

Placentation: the arrangement of placentas, and hence of ovules, within an ovary.

  • Axile placenta: Pertaining to an axis, as of a placenta along the central axis in a compound ovary with more than one chamber.
  • Parietal placentas: Pertaining to placentas on the inside surface of the ovary wall in a compound ovary with one or more chambers.
  • free-central and basal placenta: Pertaining to a placenta along the central axis in a compound ovary with only one chamber.

Two hypothesis of the evolution of ovary placentation.

 

Cross section and longitudinal section of Viola cornuta hybrid ovary. note the three parietal placentas

 

Fruit

A ripened ovary and sometimes associated structures. A simple fruit develops from one ovary - e.g. cherry, apple, the later derived largely from the hypanthium; multiple and compound fruits develop from ovaries of one and more than one flower, respectively, held together as a unit. - e.g. a strawberry is an multiple fruit of achenes or achenetum held together by a juicy, red flower receptacle; a fig is a compound fruit of achenes surrounded by a fleshy inflorescence receptacle.

 

Fruits (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

 

Achene: Dry indehiscent, 1-seeded fruit from a 1- chambered ovary, often appearing to be a naked seed.

Samara: A dry, indehiscent flattened fruit characterized by a pericarp that is compressed to the surface of one or more seeds and forming a wing at the margins longer than the lenght of the seeded portion.

Camara: An indehiscent or tardily dehiscent fruit composed of one carpel.

 

Samara, Achene and Camara (Spjut, R.W. 'A Systematic Treatment of Fruit Types' 1994)

 

Berry: Fleshy, indehiscent fruit in which the seeds are not encased in a stone and are generally more than 1.

Drupe: Fleshy or pulpy, indehiscent, superficially berry-like fruit with one seed encased in a hardened stone that is derived from inner ovary tissue (sometimes several seeds are encased seperately or together).

 

Berry, Drupe (Spjut, R.W. 'A Systematic Treatment of Fruit Types' 1994)

 

Follicle: Dry generally many-seeded fruit from a simple pistil, dehiscent on only one side, along a single suture. A flower may have a simple fruit of 1 follicle or a multiple fruit of several follicles as follicetum.

Coccum: A simple dehiscent fruit consisting of one carpel that opens along two sutures and contains one to several basally attached seeds, not belonging to the Fabales.

Lomentum: Fruit composed of a single carpel that disarticulates into seed-bearing segments.

 

 

Follicle, Coccum and Lomentum (Spjut, R.W. 'A Systematic Treatment of Fruit Types' 1994)

 

Coccum: A simple dehiscent fruit consisting of one carpel that opens along two sutures and contains one to several basally attached seeds, not belonging to the Fabales.

Lomentum: Fruit composed of a single carpel that disarticulates into seed-bearing segments.

Legume: In Fabaceae, a dry somewhat flesy, one- to many seeded fruit from a simple pistil, typically dehiscent longitudinally along two sutures and splitting into halves that remain joined at the base, sometimes indehiscent or breaking crosswise into one-seeded segements.

Nut: A mostly dry, indehiscent fruit in which a single seed is encased in a hard shell that is derived from inner ovary tissue.

Nutlet: Small schizocarp fruit, dry nut (or nut-like fruit), generally one of several produced by a single flower. (example Boraginaceae, Lamiaceae...)

Pome: In Rosaceae, a fleshy, indehiscent fruit, such as an apple or pear. Derived from a compound, inferior ovary (the core and inner felshy material) and its surrounding hypanthium (outer fleshy material and skin)

Capsule: dry, generally many-seeded fruit from compound pistil, nearly always dehiscent (irregularly or by pores, slits, or lines of separation).

  • loculicidal: longitudinally dehiscent through the ovary wall at or near the center of each chamber.
  • septicidal: dehiscent longitudinally through the ovary wall at or near the centre of each septum, such that each resulting valve or segment corresponds to a single chamber.
  • septifragal: longitudinally dehiscent through the ovary wall at each side of the spetum, such than the septum with the seeds will be exposed and the valves detached.
  • circumscissille: Dehiscent by a transverse line, the top coming off as a lid.
  • poricide: Dehiscent by pores at the top of the capsule e.g. Papaver

 

Seed

A fertilized ovule, the earliest product of sexual reproduction in plants. A seed is attached to the placenta by the funiculus and the scar left on the seed is called the Hilum. The micropyle is the entry chanel for the pollen tube to reach the ovule.

Often seeds have fleshy appendage to atract disseminators: Caruncle, Arillode or Aril.

The ovule can be orthotropous or anatropous if it is upside down and bent along the funiculus.

 

Seed morphology (Adrian D.Bell 'Plant Form' new ed. Timber press 2008)

Floral Formulae

A floral formulae is a convenient method of recording floral symetry, number of parts, connation and adnation, insertion and ovary position. Find below method copied from Prenner et al. 2010. 'Floral formulae updated for routine inclusion in formal taxonomic description' TAXON 59(1): 241-250

Symetry
median monosymetry Unicode: 2193  ↓
transverse monosymetry  Unicode: 2192 →
Ø  oblique monosymetry Unicode: 00D8 Ø
┼ disymetry Unicode: 253C ┼
*polysymetry  asterisk
asymmetry Unicode: 2202 ∂

Organs
B bracteates (flower in the axil of subtending bract)
Bt Bracteolate (flower preceded by bracteole/s)
K calyx (number of sepals) (superscript=sepaloid organ)
C corolla (number of petals) (superscript = petaloid organ)
P perigon (number of tepals)
A androecium (number of stamen)
AX∞ stamen fascicles (X=number of fascicles, highlighted with superscript infinity symbol)
AX↔X obdiplostemonous androecium (X=number of stamens per whorl, connected by ‘left right arrow’; Unicode 2194)
AX↔ obhaplostemonous androecium (X=number of stamens followed by ‘left right arrow’; Unicode 2194)
G gynoecium (number of carpels)
G superior ovary
-G- half-inferior ovary
Ĝ inferior ovary (Unicode 011C)
V number of ovules per ovary
Va apical placentation
Vb basal placentation
Vc free central placentation
Vm marginal placentation
Vp parietal placentation
Vx axile placentation
® resupination (Unicode 00AE)

Others
‘many’ organs (i.e., >12) (Unicode 221E)
defined range of organ number (en-dash Unicode 2013)
+(plus) connects different whorls of the same organ category
: (colon) seperates morphologically contrasting organs with one organ whorl
(x), [x], {x} fusion of different organs (different kinds of bracket allow for a nested series of up to three levels of fused organs)
r organ reduction (superscript r) r
0 organ loss (superscript zero)
♀ female (pistillate) flower (Unicode 2640)
♂ male (staminate) flower (Unicode 2642)

 

K5* C5↓ A3+2↓ G (3)↓Vx∞

Floral formula of Viola cornuta hybrid

insert Gerhard list here. Prenner et al. 2010. 'Floral formulae updated for routine inclusion in formal taxonomic description' TAXON 59(1): 241-250

Floral Diagram

A floral Diagram is a more graphic way to record floral morphology.

 

Floral diagram of Viola cornuta hybrid

Family glossary

Some families, especially large ones like Asteraceae and Poaceae or 'non flowering' families like Ferns will have a large number of terms only used to describe morphology of plants in those families.

 

Fern glossary (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

 

Asteraceae glossary (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

 

Poaceae glossary (Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993)

 

Bibliography

Adrian D.Bell 'Plant Form' new ed. Timber press 2008

B & T world seeds glossary http://b-and-t-world-seeds.com/botgloss.htm

Hickman, C. 'The Jepson Manual Higher Plants of California drawing by Linda Ann Vorobic et al. 1993

Spjut, R.W. 'A Systematic Treatment of Fruit Types' 1994.

 

Home page

Morphology teaching in the past

Habit

Roots

Stems

Leaves

Indumentum

Inflorescence

Flowers

Fruit

Seed

Floral Formula

Floral Diagram

Family glossary

Bibliography

Keys

Matrix

Dichotomous Key

Dichotomous key 2

Multi Access Key

Punched Cards

Hommogram

 

     

A Botanical key is a tool to allow quick and easy identification of species. There are several types of keys, shown below some examples.

Matrix

 

Mealy leaves

Common flowering stem

Corolla colour

Calyx

Fruit

Primula farinosa

Yes

No

lilac

Pale green

Slightly longer than calyx

Primula scotica

Yes

No

violet

Pale green

Longer than calyx

Primula verris

No

long

yellow

Pale green

Enclosed in the calyx

Primula elatior

No

long

yellow

Green with darker midribs.

Projecting out.

Primula vulgaris

No

Very short

yellow

Pale green

Slightly longer than calyx

Dichotomous Key

1Leaves mealy beneath; flowers lilac or purple……………….....…………………2
Leaves not mealy beneath; flowers yellow…………………................………….3


2 Corolla lilac, 1cm or more in diameter; fruit slightly longer than the calyx …………………………………………………………........................ .P.farinosa
Corolla violet-purple, less than 1cm in diameter; fruit much longer than the calyx ……………………………………………………………….........………..._______


3 Common flowering stem clearly present; flowers rarely more than 20 mm in diameter …..................................................................................................………4
Common flowering stem very short or absent; flowers +/- 30 mm in diameter ....................................................................................... ……....________


4 Calyx pale green all over; fruit enclosed in calyx……………….…________
Calyx with the mid-ribs much darker green than the remainder; fruit projecting out of the calyx ……………………………………………………….................…._______

 

Dichotomous Key 2

Leaves mealy beneath; flowers lilac or purple
Corolla lilac, 1cm or more in diameter; fruit slightly longer than the calyx …………………………………………………………...........……….._________
Corolla violet-purple, less than 1cm in diameter; fruit much longer than the calyx …………………………………………………............................…..__________


Leaves not mealy beneath; flowers yellow
Common flowering stem clearly present; flowers rarely more than 20 mm in diameter
Calyx pale green all over; fruit enclosed in calyx ........__________
Calyx with the mid-ribs much darker green than the remainder; fruit projecting out of the calyx …………………………………………………..........................….__________
Common flowering stem very short or absent; flowers +/- 30 mm in diameter ………………………………………………………........................……__________

Multi access Key

A: Mealy leaves
B: Leaves not mealy beneath
C: common flowering stem
D: no common flowering stem
E: Corolla lilac
F: Corolla violet
G: Corolla yellow
H: Calyx pale green
I: Calyx with darker midribs.
J: Capsule projecting out the calyx
K: Calyx not projecting out the calyx

_ _ _ _ _ = Primula farinosa

BCGHK = Primula vulgaris

ADFHK = ___________

_ _ _ _ _ = Primula elatior

BCGHK = ___________

Punched Cards

 

Hommogram

 

Keys

Matrix

Dichotomous Key

Dichotomous key 2

Multi Access Key

Punched Cards

Hommogram